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the minds of many and lead to project funding and construction. In 1973, final closure of the dam was made and the facility became capable of storing tributary flood waters. Chatfield Dam is located approximately 0.5 mile above the City of Littleton, Colorado, in Douglas and Jefferson Counties. In addition to the Cherry Creek, Mt. Carbon and Chatfield Dams, one additional flood control measure, the Bear Creek Dam, was envisioned in the early 1940s. Authorization for funding and design of the dam did not occur until 1968. Construction on the $68 million earthfill structure was started in July 1974, and it is scheduled to be fully operational in 1979. The dam will be 170 feet high and approximately 7000 feet wide, having a storage capacity of 75,000 acre-feet. . Throughout the study segment of the South Platte River in Adams County, levees have also been constructed as a flood protection measure. Photographic evidence of the South Platte River floods of 1965 and 1973 (References 2 and 3), however, show these levees to be ineffective against laO-year frequency floods. On large segments of the South Platte River, historical records indicate that the 1965 and 1973 floods were of the lOa-year magnitude or greater. . A major drainageway planning report has been completed for Big Dry Creek (Reference 4). This report designates various structural measures and non-structural actions which would be appropriate to alleviate potential flood damage along this stream. The Urban Drainage and Flood Control District has carried out numerous planning studias and has various projects under way to reduce flooding in Adams County (References 4 through 9). These include projects on Niver Creek, First Creek, Hidden Lake, and Grange Hall Creek. The lOa-year flood plain along the lower reach of Niver Creek has been reduced by channel improvements and will be further reduced by storm-water detention facilities at Interstate 25; these structures are under construction. Master planning studies have been completed for Hidden Lake, First Cre~~, Little Dry Creek, and Grange Hall Creek which will propose ways of reducing flooding problems. A flood hazard area delineation study is underway for Clear Creek. 3.0 ENGINEERING METHODS . For flooding sources studied in detail in Adams County, standard hydro- logic and hydraulic study methods were used to determine the flood hazard data required for this study. Flqods having recurrence intervals of 10, 50, 100, and 500 years have been selected as having special significance for flood plain management and for flood insurance premium rates. The analyses reported here reflect current conditions in the watersheds of the streams. 13 .j i j